Figure 2

 In situ  hybridization with  SOX9  on autopods of  Talpa occidentalis  ,  Cryptotis parva  and  Mus musculus  . Right hands and feet are in dorsal view, except for O-P, which are left hand and foot in palmar and plantar view, respectively [4]. Images E-N and Q-R were mirrored to make the orientation consistent. Roman numbers indicate digits. Age determination: early 17 d (A-B), 18d (C-D), 19d (E-F), 13.5d (G-H), 15.5d (I-J), 17.5d (K-L), 12.5d (M-N), 13.5d (O-P), and 14.5 d (Q-R).